Two-Piece Bearing Housing For A Centrifugal Pump

ABSTRACT

A two-piece bearing housing is provided for use in centrifugal pumps having or requiring multiple chambers for enclosing or confining bearings or seals, and/or providing lubricant or coolant to the bearings and seals of the pump, the two-piece housing providing several improvements including the ability to make the two pieces from different materials, the reduction in scrap castings due to imprecision achieved in the casting process and improved structures in the housing for monitoring the lubricant chambers in the housing.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional application claiming priority toprovisional patent application Ser. No. 60/927,594 filed May 4, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to centrifugal pumps and relatesspecifically to a two-piece bearing housing for use in a centrifugalpump.

2. Description of Related Art

Centrifugal pumps generally comprise a pump casing in which an impelleris positioned to rotate for the processing of fluid material. Theimpeller, which is connected to a drive shaft, is part of a rotatingassembly that further comprises the drive shaft, ball bearings, seals, amechanical shaft seal and various associated hardware. The rotatingassembly is bolted to the pump casing in a manner that facilitatesremoval of the rotating assembly for repair or replacement. Further, abearing housing is provided to house the drive shaft, at least one setof bearings and associated seals that support and isolate the driveshaft.

A bearing housing may be comprised of two chambers, including thebearing oil chamber and the mechanical seal oil chamber. The bearing oilchamber houses bearings for the drive shaft and is separately providedwith lubricating fluid for the bearings. The mechanical seal oil chamberis typically isolated from the bearing oil chamber and is provided witha separate source of lubrication to lubricate the lip seals andmechanical shaft seal about the impeller.

The bearing housing of conventional centrifugal pumps is made of a onepiece casting. In certain types of bearing housings, the casting of theone-piece bearing housing is complicated by the existence of theseparate bearing oil chamber and the mechanical seal oil chamber. Thatis, two sand cores are made corresponding to the two separate oilchambers. The two sand cores are then positioned in a larger moldcorresponding to the outer housing. Molten metal is then poured into themold and about the two sand cores to produce the casting of the bearinghousing.

The manufacture of a one-piece bearing housing is made difficult by theexacting placement of the two sand cores in order to provide theseparate oil chambers. Additionally, it is difficult to get the moltenmetal to flow into the inner walls of the mold to form the wall whichseparates the two chambers.

Moreover, a gas is produced by the sand core material during the castingprocess when the core material is contacted with the molten metal. Ifthe gas cannot escape the mold, it forms undesirable porosities in thewall of the casting.

The porosities essentially represent leaks through the wall of thecasting and can be from moderate to severe in the degree to which theporosities extend into or through the wall of the casting. The existenceof the porosities result in a certain number of castings being unusable,which increases the scrap rate for the casting process. The overall costof the castings is increased proportionally to the amount of scrap thatis produced through bad castings.

A further problem encountered with the present one-piece casting ofbearing housings is the fact that core sand is difficult to extract fromthe casting. Additionally, metal chips resulting from the machining ofthe casting are difficult to remove from the casting. Consequently, agreat deal of time and cost is spent attempting to produce a castingthat is free of residual sand and metal chips, and attempts to removemetal chips and sand from the casting may not be entirely successful.

An additional cost concern relating to conventional one-piece bearinghousings is the fact that the bearing housing is made of, for example,stainless steel when the pump is going to be used for more corrosiveslurry processing. As such, the bearing housing must be made entirelyfrom stainless steel due to the casting process. Because of the unitary,or one piece casting, no cost benefit can be derived from making part ofthe bearing housing from another, less costly metal material.

Thus, it would be advantageous in the centrifugal pump industry toprovide a bearing housing that is more easily produced and with moreaccuracy, thereby reducing the amount of scrap castings. It would alsobe advantageous to provide a bearing housing that can be made fromdifferent metals to reduce the overall cost of the casting process andthereby reduce the cost of the pump and its operation.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, a bearing housing for acentrifugal pump is formed in two-pieces, which facilitates themanufacture of the bearing housing, enables the bearing housing to bemade of disparate types of materials and significantly reduces theamount of scrap castings. While the bearing housing of the presentinvention is described in terms of use in a self-priming pump, it ispossible to adapt the two-piece bearing housing of the present inventionfor use in other types of centrifugal pumps that have multiple bearinghousing and/or multiple lubricant chamber arrangements.

The two-piece bearing housing of the present invention may beparticularly directed to those types of bearing housings where oneportion of the housing contains the bearings for the drive shaft of thepump, and that portion is positioned, housed or nested within anotherportion of the bearing housing.

The two-piece bearing housing of the present invention provides many andsignificant advantages over known bearing housings having two chamberhousings. Principally, the present invention enables the two housings tobe molded separately, thereby eliminating the need for the exactingprecision required in making castings of one-piece bearing housings. Thetwo-piece construction further eliminates small openings in the housingwhere gases can form during the casting process which leads toundesirable porosities in the casting. The amount of scrap castings isreduced as a result.

The two-piece construction further allows the two pieces to be made ofdifferent materials, thereby reducing the overall cost of the bearinghousing and pump. The two-piece construction also facilitates repair andreplacement, with a concomitant savings in repair costs since only onepiece of the housing may need to be repaired or replaced, rather thanrequiring replacement of the entire bearing housing.

The configuration of the two-piece bearing housing of the presentinvention provides improved features over the conventional one-piecebearing housing. Specifically, the windows provided in the bearinghousing for viewing the lubricant chambers are positioned away from thecenterline of the pump, thereby facilitating viewing of the lubricantlevels in the chambers during operation of the pump. The atmosphericchamber port is also advantageously provided away from the centerline ofthe pump to facilitate the critical monitoring of leakage from thebearing housing.

These and other advantages of the bearing housing of the presentinvention will become apparent in the exemplar description providedfurther below, and in the drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, which currently illustrate the best mode for carryingout the invention:

FIG. 1 is a view in cross section of a conventional self-priming pumpillustrating a prior art bearing housing of one-piece construction, andits positioning within the pump;

FIG. 2 is a view in cross section of the rotating assembly of the pumpshown in FIG. 1;

FIG. 3 is a view in cross section of the conventional one-piece bearinghousing shown in FIG. 2, without the rotating elements, and shownrotated 180° in orientation from the view shown in FIG. 2;

FIG. 4 is a view in cross section of the two-piece bearing housing ofthe present invention as part of the rotating assembly of a pump;

FIG. 5 is a view in cross section of the two-piece bearing housing shownin FIG. 4, without the rotating elements, and shown rotated 180° inorientation from the view shown in FIG. 4;

FIG. 6 is a view of the outboard end of the pump shown in FIG. 1 havinga one-piece bearing housing and depicting the conventional placement ofview windows into the bearing chambers;

FIG. 7 is a view of the outboard end of a pump having a two-piecebearing housing and depicting the placement of view windows into thebearing chambers in the present invention;

FIG. 8A is a view in partial cross section of the one-piece bearinghousing shown in FIG. 3 taken at line 8-8;

FIG. 8B is a perspective view in cross section of the conventionalone-piece bearing housing showing positioning of the atmospheric chamberdrain port;

FIG. 9A is a view in partial cross section of the two-piece bearinghousing of the present invention shown in FIG. 9B, taken at line A-A;

FIG. 9B is a perspective view in cross section of the bearing housing ofthe present invention depicting the arrangement and placement of theatmospheric chamber drain port;

FIG. 10 is a perspective view of the one-piece bearing housing shown inFIG. 8B, depicting both the outer housing and the cross sectional viewof the bearing housing; and

FIG. 11 is an exploded view of the two-piece bearing housing of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a self-priming centrifugal pump 10 of the prior arthaving a single-piece construction of the bearing housing 12.Self-priming pumps are well-known in the art and a description of theoverall structure of the pump is not required here for the understandingof the present invention. The bearing housing 12 is part of the rotatingassembly 14, which further comprises the impeller 16, the drive shaft 18to which the impeller 16 is attached by an impeller bolt 20, amechanical shaft seal 24, lip seals 26, forward bearing 28, rear bearing30 and the bearing cap 32.

The impeller 16 is spaced from the bearing housing 12 by a seal plate 36that is secured against the pump casing 38 and which provides a housingfor the mechanical shaft seal 24. The mechanical shaft seal 24 surroundsthe drive shaft 18 to seal against fluid leaks from the pump chamber 39.The lip seals 26 also surround the drive shaft 18 and seal the bearings28, 30 housed within the bearing housing 12. The bearing cap 32 and lipseal 34 also surround the drive shaft 18 at the outboard end to seal thebearing housing 12.

As may be viewed more specifically in FIG. 2, which illustrates just therotating assembly 14 and seal plate 36 of a conventional, single-piecebearing housing 12, the bearing housing 12 is constructed with amechanical seal oil chamber 40 and a bearing oil chamber 42 which ishoused or nested within the mechanical seal oil chamber 40. Themechanical seal oil chamber 40 contains fluid lubricant for cooling andlubricating the mechanical seal 24. The lubricant is introduced into themechanical seal oil chamber 40 through an inlet 44.

The bearing oil chamber 42 also contains fluid lubricant for cooling andlubricating the forward bearing 28 and the rear bearing 30. The bearingoil chamber 42 is filled through an inlet 46.

FIG. 3 illustrates further the construction of a single-piece bearinghousing 12 of the prior art. Notably, the prior art bearing housing 12illustrated in FIG. 3, when referenced against the same bearing housing12 shown in FIGS. 1 and 2, is rotated 180° about an axis perpendicularto the central axis of the rotating assembly 14 corresponding to thedrive shaft 18. FIG. 3 better depicts the construction of theconventional bearing housing 12 itself and provides a betterillustration of the complexities of forming the single-piece bearinghousing 12. Reference may also be made to FIGS. 8A and 8B and FIG. 10,which are perspective views of a single-piece bearing housing 12, toillustrate the configuration and manufacturing complexities.

In forming the single-piece bearing housing 12, a solid sand core isused which corresponds to the mechanical seal oil chamber and thebearing oil chamber. The solid sand core, in accordance with knowncasting techniques, is positioned within a mold the configuration ofwhich corresponds with the outer shape of the bearing housing 12. Thesolid sand core must be positioned precisely in the mold for formationof the casting. Molten metal is then poured into the mold and about thesolid sand core to produce the casting of the bearing housing 12, asillustrated in FIG. 3 and FIG. 8B.

When the metal has cooled and the casting has solidified or cured, thesand core is removed and the casting is further machined to provide theinlets 44, 46 into the mechanical seal oil chamber 40 and the bearingoil chamber 42, respectively. Atmospheric barrier drain port 48 anddrain bore 50 are also machined to form drain conduits for the lip seals26 (FIG. 1) and mechanical seal oil chamber 40, respectively.

As previously noted, the placement of the sand core in the mold forcasting the conventional single-piece bearing housing is verycomplicated and requires precision that, if not achieved, can introduceerrors into the casting process. Additionally, a gas is often producedwhen the molten metal contacts the sand core which results in porositiesbeing formed in the casting. The porosities represent breaches in thewall of the bearing housing casting which can lead to failure of thebearing housing. Therefore, castings with too many or very severeporosities must be scrapped and the resulting cost of casting productionis significantly increased.

The present invention is, therefore, directed to overcoming the numerousand heretofore insoluble problems encountered with producingconventional single-piece bearing housings. In accordance with thepresent invention, a two-piece bearing housing 60 is provided whichovercomes these problems and represents a significant improvement in thepump casting art. The two-piece bearing housing of the present inventionis illustrated in FIGS. 4, 5, 9A, 9B and 11. Structures of the presentinvention which are common to structures known in the prior artsingle-piece bearing housing 12 are denoted with the same referencenumeral for clarity of comparison and description.

As depicted in FIGS. 4 and 5 (noting that the view in FIG. 5 is turned180° from the view shown in FIG. 4), the bearing housing 60 of thepresent invention comprises two pieces, an outer housing 62 and an innerhousing 64, which are separately formed through known sand core castingprocesses. The outer housing 62 has a first end 68 which is positionedto contact the seal plate 36 of the pump 10 and a second end 70 againstwhich the inner housing 64 is securely positioned.

The outer housing 62 is secured to the inner housing 64 by anyappropriate means. As depicted in FIG. 5, the outer housing 62 may besecured to the inner housing 64 by bolts positioned through the secondend 70 of the outer housing 62. An o-ring 72 is positioned between theouter housing 62 and inner housing 64 to seal the two housings. Theinner housing 64 has a first end 74 which is oriented for positioningadjacent the seal plate 36 and a second end 76 to which the bearing cap32 is attached.

The inner housing 64 is nested within the outer housing 62 when thetwo-pieces are joined. The outer housing 62 and inner housing 64 areconcentrically positioned, having a common centerline which correspondswith the positioning of the drive shaft of the pump through the bearinghousing 60. The outer housing 62 of the present invention provides themechanical seal oil chamber 80 of the bearing housing 60 by formation ofa space between the outer housing 62 and the inner housing 64. The innerhousing 64 provides an inner space that defines the bearing oil chamber82 of the bearing housing 60.

The separate formation of the outer housing 62 and inner housing 64 ofthe bearing housing 60 of the present invention provides severaladvantages heretofore unknown or unavailable to the conventionalone-piece bearing housing construction. While the casting of the twopieces of the present invention still involves sand core castingprocesses, the two sand cores corresponding to the outer housing 62 andthe inner housing 64 are easy to position in the mold for casting, andmore precise castings can be achieved.

Additionally, the separate cores of the present invention eliminate anyinternal walls (i.e., the wall of the bearing oil chamber in asingle-piece casting) thereby eliminating the difficulty encountered inreleasing trapped gases formed in the single-piece construction thatleads to undesirable porosities. As a result, the number of scrapcastings is significantly reduced. This advantage provides not only asignificant cost saving, but an environmental advantage in not having todispose of discarded castings.

The respective oil chambers 80, 82 of the two-piece housing 60 have beendesigned to increase the oil capacity by as much as fifteen totwenty-five percent over conventional one-piece housings. Consequently,more cooling capacity is provided to the bearings and more lubricationcapacity is provided to the mechanical shaft seal. The increasedlubrication capacity increases the length of time the pump can remain inoperation should the seals start to fail because of the increasedlubrication that is available.

The larger openings and simplified cores of the casting process in thepresent invention enable sand to be more easily and completely removed,and the metal chips are more easily removed after machining. Machiningand manufacturing costs are reduced as a result.

An even greater advantage in the present invention is realized in theability to make the outer housing 62 casting and the inner housing 64casting from different materials. That is, when especially corrosiveand/or abrasive fluids are being processed by a pump, those portions ofthe pump that come in contact with the corrosive and/or abrasive fluidmust be made of materials which are specially selected to resistcorrosion or wear. Such materials may typically include stainless steeland high chrome alloys. Such materials are significantly more expensivedue to their improved properties.

The mechanical seal oil chamber 80 is potentially subject to contactwith the fluid being pumped and, therefore, it may be necessary ordesirable to cast the outer housing 62 from an appropriate material thatis capable of withstanding contact with the corrosive and/or abrasivefluid. However, the bearing oil chamber 82 is not subject to contactwith the fluid being pumped and the inner housing 64 may, therefore, bemade of less expensive material. The ability to cast the outer housing62 separate from the inner housing 64, therefore, provides castingchoices which reduce the manufacturing costs of the pump.

A further advantage of the present invention is realized in that theouter housing 62 of the present invention essentially is rendered anon-wear component given the ability to make the outer housing 62 ofmore corrosion-resistant material. A bearing failure in the presentinvention requires only a replacement of the less expensive innerhousing 64 rather than replacement of the entire bearing housing 12 asis known in the conventional one-piece construction. This advantageprovides not only a cost savings, but an environmental advantage.

Yet another significant advantage is realized in that the outer housing62 alone can be replaced in the event that it becomes damaged, forexample, in the course of normal operation due to abrasion and/orcorrosion. The outer housing 62 can be replaced without the need toreplace the inner bearing housing 64, and more significantly, the outerhousing can be replaced without affecting the integrity of the bearings.

The ability to make the outer housing 62 of hard materials also has asignificant advantage in that the tight machining tolerances (+/−0.0003)for the bearing housing 60 are required in the inner housing 64 orbearing oil chamber 82, not in the hard material outer housing 62.Machining bores with tight tolerances is much more difficult in hardmaterials than in soft materials, such as cast iron, which is what theinner housing 64 may typically be made of.

The two-piece bearing housing 60 of the present invention comprises anadvantageous design element that is a further improvement overconventional one-piece bearing housings 12, as best illustrated in FIGS.6 and 7. It can be seen from FIG. 6 that the conventional bearinghousing 12 is provided with a window 86 for viewing the lubricant levelin the mechanical seal oil chamber 40 and a window 88 for viewing thelubricant level in the bearing oil chamber 42 while the pump is inoperation. Both windows 86, 88 of the conventional bearing housing areoriented along the axis of the pump and face the drive shaft couplings,which makes viewing the respective chambers 40, 42 very difficult whenthe drive shaft is rotating and the pump is running.

As illustrated in FIG. 7, the two-piece bearing housing 60 is structuredwith a window positioned through the inner housing 64 to enable viewingof the mechanical seal oil chamber 80 of the outer housing 62. A window92 is also formed through the inner housing 64 to enable viewing of thebearing oil chamber 82 within the inner housing 64. Both windows 90, 92are positioned at an angle to the centerline of the bearing housing 60,and thus the axis of the pump, which enables easier viewing of therespective oil chambers when the pump is in operation.

FIGS. 8A and 8B demonstrate a further disadvantage of known one-piecebearing housings. Specifically, FIG. 8A illustrates that in theconventional single-piece bearing housing 12, the atmospheric barrierdrain port 48 is positioned parallel to the centerline of the pump andbelow the position of the drive shaft, which renders viewing of theouter opening 49, shown in FIG. 8B, of the drain port 48 very difficultwhen the pump is assembled and in operation. Leakage of fluid from theatmospheric barrier drain port 48 is an indication of bearing failureand is critical to proper monitoring and maintenance of the pump.

FIGS. 9A and 9B illustrate that in the present invention, theatmospheric barrier drain port 94 is positioned at an angle to thecenterline of the bearing housing 60 and is directed away from the driveshaft so that the exterior opening 96 is positioned laterally or to theside of the drive shaft making the drain port easily visible from theside of the pump when assembled and in operation. The ability to readilyobserve leakage through the atmospheric barrier drain port 94 enablestimely replacement of the inner housing 64 or bearing housing. Theangled position of the drain ports also facilitates easy access whenchanging the lubricants in the pump.

The two-piece bearing housing of the present invention is particularlysuited for use in any centrifugal pump having seal and/or bearingrequirements where the housing provided for the bearings and/or sealsmay employ multiple chambers that may also serve as lubricant-containingchambers, and where the housing is traditionally made in a singleconfiguration. The two-piece bearing housing is adaptable to any numberof pump applications. Hence, reference herein to specific details of thehousing configuration is by way of example only and not by way oflimitation.

1-17. (canceled)
 18. A bearing housing for a centrifugal pump,comprising: an outer housing forming a chamber which is structured toretain a fluid for lubricating or cooling the sealing elements of acentrifugal pump; and a separately formed inner housing sized forpositioning within said chamber of said outer housing and being axiallyaligned with said outer housing, said inner housing forming a chamberfor retaining a fluid for lubricating or cooling elements of therotating assembly of the centrifugal pump, said inner housing having awindow formed through said inner housing for observation of said chamberformed by said outer housing, the window being oriented at an angle to adefined centerline of the bearing housing and said inner housing havingmeans for detachable securement to said outer housing.
 19. The bearinghousing of claim 18 further comprising a window formed through saidinner housing oriented for observation of the chamber within the innerhousing, said window being oriented at an angle to a defined centerlineof said bearing housing.
 20. The bearing housing of claim 18 whereinsaid outer housing is made of a different material than the materialfrom which said inner housing is formed.
 21. The bearing housing ofclaim 20 wherein said outer housing is formed from material that has ahigher measurement of hardness than the material from which said innerhousing is made.
 22. A centrifugal pump having a pump casing and a driveshaft positioned through said pump casing to support an impellerpositioned within the pump casing, said centrifugal pump furthercomprising a bearing housing having an outer housing forming a chamberwhich is structured to retain a fluid for lubricating or cooling thesealing elements of the centrifugal pump and a separately formed innerhousing sized for positioning within said chamber of said outer housingand being axially aligned with said outer housing, said inner housingforming a chamber for retaining a fluid for lubricating or coolingelements of the rotating assembly of the centrifugal pump, said innerhousing having means for detachable securement to said outer housing andsaid inner housing having a window formed through said inner housingoriented for enabling observation into said chamber formed between saidouter housing and said inner housing, said window being oriented at anangle to a centerline of said centrifugal pump defined by the axis ofthe drive shaft.
 23. The centrifugal pump of claim 22 wherein saidchamber in said outer housing is a mechanical seal oil chamber.
 24. Thecentrifugal pump of claim 22 wherein said chamber in said inner housingis a bearing oil chamber.
 25. The centrifugal pump of claim 22 whereinsaid outer housing of said bearing housing is made of a differentmaterial than the material from which said inner housing is formed. 26.The centrifugal pump of claim 25 wherein said outer housing is formedfrom material that has a higher measurement of hardness than thematerial from which said inner housing is made.
 27. A centrifugal pumphaving a pump casing and a drive shaft positioned through said pumpcasing to support an impeller positioned within the pump casing, saidcentrifugal pump further comprising a bearing housing having an outerhousing providing a mechanical seal oil chamber for cooling orlubricating the seals of a rotating assembly positioned through saidbearing housing and an inner housing sized for positioning within themechanical seal oil chamber of the outer housing, said inner housinghaving an internal fluid chamber positioned for cooling or lubricatingbearings of the rotating assembly and having a window formed throughsaid inner housing positioned for viewing said mechanical seal oilchamber, the outer housing and inner housing being separately formed bya separate casting process wherein said outer housing is cast using adifferent material from that material which is used to cast said innerhousing, and the outer housing and inner housing being detachably joinedtogether by securement means.
 28. The centrifugal pump of claim 27wherein said outer housing is cast from a material that has a higherdegree of hardness than the material from which the inner housing iscast.